An angular sensor is a kind of sensor that provides rotary speed and position measurements by converting angular displacements to electrical signals. Angular sensors can be found in wide array of automotive and industrial applications such as steering wheel position sensing, pedal position sensing, and motor-shaft position sensing.
A commonly known interface used for data communications of the angular sensor is an incremental interface. This kind of interface is widely used due to its low cost, high speed transmission with rather low frequency signals, and ability to provide signals that can be easily decoded to provide motion related information such as rotary speed and rotary direction. It is also compatible to optical sensors. The incremental interface may include three unidirectional channels, known as A, B, Z channels. Signal lines A and B provide phase shifted pulses indicating rotary speed and rotary direction. Channel Z provides an index pulse indicating a reference point such as a zero-crossing point of the rotation. Counting of the pulses from the Signal lines A and B is reset once the index pulse from the channel Z is received. Thus, an absolute rotary position can be determined. However, a disadvantage of this incremental interface is that it is not ‘true-power-on’. The absolute rotary position can only be received after the index pulse is received, i.e., the rotation passes the zero-crossing point. The absolute rotary position information may be delayed as the sensor may power on from a rotary position away from the zero-crossing point.